Grooving laminated plywood



May 2, E950 G. H. NORQUHST 2955359739 GROOVING LAMINATED PLYWOOD Original Filed Dec. 12, 1945 2 Sheets-Sheet l I INVENTOR [710111 E WE 115i o/MVMM y 1950 G. H. NORQUIST 2,505,789

GROOVING LAMINATED PLYWOOD Original Filed Dec. 12, 1945 2 Sheets-Sheet 2 I NVEN TOR film 1? f/Zlgm'w/ FTT RNEVB' 'tion thereof.

Patented May 2, 195% YET *GROOVING LAMINATED PLYWOOD Glenn H. Norquist, Jamestown, N. Y.

Original applicationDecember 12, 1945, Serial No.

ll Claims. i

This invention :relates to grooving laminated plywood and .more particularly to an improved grooving wheel and method of grooving laminated plywood to permitaccurate angular forma- This application is a division of my copending application Serial No. 634,432 filed December 12, 1945.

In the manufacture of numerous fabricated products from laminated plywood panels, and particularly metal cladplywood panels comprising plywood having ametal facing sheet bonded to one side thereof, it is necessary to form or out grooves extended substantially through the plywood to permit angular shaping of the panel. The plywood base sheet forming a constituent part of such metalclad panels is formed from a plurality of layers of wood or veneer, with the grain of thewood layers extending in different directions so that when the layers are bonded together as by resinous :or similar adhesives, the composite base sheet will be of substantially equal strength in all directions.

When the plywoodbase sheet is groove-cut to permit angular shaping of the sections of the plywood panel, it would normally appear that the groove should be cut to present a V-shaped cross-section with straight inclined faces and with the groove angle formed to accuratelycorrespond to the intended angular position of the panel sections as finally shaped.

to be shaped at a true 90 angle with respect to one another, it would normally appear that such shaping would be efiected if a groove having a 90 angle and presenting'straighttside faces n were cut from the composite plywood base sheet, with the expected .result that when the panel sections were shaped into their intended 90 angularrelationship, the inclined straight faces of the groove would snugly abut and form a tight hairline joint.

Such normally expected and desirable result cannot in fact be achieved where the composite base sheet is constructed of plurality of superimposed wood or veneer layers, due to the fact that the layer or layers which are severed transversely of theirgrain by the grooving tool will bloom or bush out-into the groove'oecause of the resilient character of the woodfiberswhile the cut ends of the wood layers which are cutsubstantially parallel to the grain will remain substantially as :cut. This end blooming effect, which is characteristic of wood fibers which are cut transversely of their grain, interferes with and makes impossible the shaping of the panel lf foi example, we assume that thepanel sections are intended Divided and this application January '29, 1948, Serial No. 5,042

section to the accurate angular shapeintended, unless adequate provision is :made to takecare of this blooming effect so thatthe panel. sections may be bent into their intended accurate angular relationship.

An object of this invention provides an improved grooving wheel for cutting angular shaped grooves in plywood panels, the-grooving wheel being'so formedandconstructed so as to cut the groove in such shape as to permit accurate angular shaping of the panel sections.

Another objectof this invention-is to provide an improved grooving .tool'having cutting arms so shaped and formedas to present curvilinear cutting edges designed to cut the plywood layer in a manner to permit/accurate shaping of the panel sections.

Another objector this-invention is to provide an improved method for grooving metal clad plywood. panels whereby predetermined accurate shaping of the panelsections thereof may be effected.

Another object'of this invention is to provide an improved metal ,clad laminated plywood'panel construction presenting a jointof such form as tocompensate for the blooming efiectof the transversely cut plywood layers whereby the panelsections will form into their intende-d-angular relationship.

Other objects-of this invention will become apparent as the disclosure proceeds.

Although the characteristic features of this invention will be particularly pointed out in the claims appended hereto, the invention itself, and the manner in-which it may be carried out, may be better understood-by referring to the following description taken in connection with the accompanying drawings forming -a part hereof, in which Fig. I is a fragmentary plan viewof a metal clad plywood panel wherein the plywood base sheet is formed from a plurality of laminations having thergrain thereof extending in different directions.

Fig. II is a transverse cross-sectional view of the metal clad plywood panel as the same appears when viewed along line IL-II of Fig. I.

Fig. III is a cross-sectional view of a metal clad laminated panel which has been grooved and shaped to ,provide an angular corner with the laminations in hair line abutment at the corner as they theoretically should, but factually do not, appear.

Fig. IV is a fragmentary cross-sectional view of a metal cladlplywood panel showing the panel sections shaped as they actually would appear when out by a 90 angle groove cutting wheel having straight cutting edges, this view illustrating the blooming effect characteristic of the laminated wood layer whose ends are out transversely of the grain, which blooming efiect prevents the shaping of the panel sections to their intended 90 angular relationship.

Fig. V is a, side elevational view of the improved groove cutting wheel shown as it appears when i grooving a metal clad laminated plywood panel with the grooving extending generally parallel to the inner and outer laminations and transversely of the intermediate lamination.

Fig. VI is an edge view of the groove cutting wheel in the process of cutting a groove in a metal clad laminated plywood panel.

Fig. VII is a cross-sectional view of the groove cutting wheel as the same appears when viewed along line VIIVII of Fig. V.

Fig. VIII is a fragmentary cross-sectional view of the metal clad laminated plywood panel shW- ing the cross-sectional shape of the groove when out by the improved groove cutting wheel shown in Figs. V, VI and VII; and

Fig. IX is a fragmentary cross-sectional view when the sections thereof have been shaped to their intended angular relation; and

Fig. XII is a diagrammatic illustration of the cutting edges of this improved groove cutting wheel when cutting a laminated plywood panel.

Similar reference characters refer to similar parts throughout the several views of the drawing and specification.

In order to more fully comprehend this invention, there is shown in Figs. I and II a metal clad plywood panel comprising a composite base sheet p having a metal liner sheet m bonded to the base sheet as by a suitable bonding adhesive. The

base sheet 10 comprises a plurality of layers or laminations of wood designated for purpose of description as layers l, 2 and 3. The grain of the exterior wood layers l and 3 are shown as extending in substantially the same direction, while the 'grain of the intermediate wood layer 2 is shown as running substantially at right angles to the run of the grain in wood layers I and 3. The wood layers l, 2 and 3 are bonded together by a selected bonding adhesive, which may be a phenolic or a urea resin compound, to provide a strong composite plywood panel which has substantially equal strength in all directions.

It has heretofore been the practice in the rooving of metal clad laminated plywood panels to use a grooving tool or wheel having straight cutting faces which normally would be expected to cut and form a groove with straight inclined faces, as would be the case if such cutting tool were used to cut an integral wood block. However in actual practice a grooving tool or wheel having straight cutting faces does not take care of the blooming efiect characteristic of the cut 4 ends of the wood layers cut transversely of the grain run, with the result that the panel sections cannot be accurately bent or shaped into their intended angular relationship.

For example, by the use of a groove cutting tool with straight cutting faces, it would normally be expected that the groove cut would have a crosssection as shown at A in Fig. II, which groove cut substantially severs the wood layers l, 2 and 3 comprising the base sheet, the bottom valley of the groove being substantially adjacent the inside face of the metal facing sheet m, and with the groove ends I, 2' and 3' of the wood layers inclined substantially along a straight line. The groove A thus illustrated is imaginary, and would not be attained in practice since the transversely cut ends of the intermediate wood layer 2 would bloom or brush out and would not lie in straight alignment with the cut ends of the wood layers I and 3 whose grain runs substantially parallel to the sides of the groove. Assuming however that the blooming phenomena of the transversely cut fibers were not encountered, then a hypothetical groove A as shown in Fig. II presenting a true angle, would permit the panel sections to be bent to their intended 90 angular shape as illustrated in Fig. III, and the inclined faces I, 2 and 3' of the groove would be in hairline abutment as shown at :c in Fig. III.

Where one of the laminated wood layers are transversely severed, a grooving tool or wheel having straight cutting faces will not produce a groove having the cross-sectional shape A as shown in Fig. II and will not permit formation of a hairline joint as as shown in Fig. III, but will produce a groove of the shape indicated at A of Fig. II wherein the transversely cut layer 2 will bloom or brush out into the groove, leaving a bloomed or brushed out end 2" extending into the groove and not in alignment with the straight out faces l and 3' of the woo-d layers 1 and 3 which are out in the general direction of the grain run. The bloomed ends 2" of the transversely cut layer 2 will prevent the bending and shaping of the panel sections into their intended angular shape.

For example, assuming that the grooving tool having straight cutting faces presenting a 90 angle is used to cut the laminated plywood base sheet, a groove having the cross-sectional contour designated as A will be produced, and when the panel sections are thereafter bent to an intended 90 relationship, the actual result will be as illustrated in Fig. IV, wherein it will be noted that the bloomed ends 2' of the intermediate layer will be in abutment before the panel sections have been shaped into their intended accurate angular relationship, forming a joint and the intended accurate angular relationship of panel sections cannot therefore be achieved.

In accordance with this invention, an improved groove cutting wheel is provided which produces a groove presenting a cross section having arcuate shape inclined faces so that the bloomed ends of the transversely cut layers will not interfere with the intended accurate shaping of the panel sections. As shown more particularly in Figs. V, VI, and VII, the improved groove cutting wheel ill is made of tool steel and comprises a hub section H secured to any desirable drive shaft l2 as by spline 52. A plurality of paired cutting arms, shown in Figs. V and VI as four in number and designated as arms [3, I4, l5 and It, extend outwardly from and are formed integrally with the hub section ll. Each cuttingarm is generally tapered from the *hub section l outwardly, the outer peripherypresenting arelatively sharped'ge l8, the edge 18 lyingin a circular arc whose center is therotative axis or'the hub section I i.

The rear or following tace 2B of each of the cutting arms is inclined rearwardly .withrespeot to thedireotion-of rotation and'the front or advancing face 21 of each cutting arm is inclined forwardly in direction of rotation. The front advancing face 2:! of each arm carriesa nib inset "22 made of suitable cutlery steel or tungsten carbide, the nib inset being braised, welded or otherwise fixedly secured so as to forman integral part of the cutting arm. The front or advancing face 2% of the nib inset is relatively r-fiat and is inclined forwardly in the directionof rotation in a plane which is substantially tangent to the shaft hole in the hubsection l l.

The advancing face of the nib inset 22 is also sloped in a plane extending diagonally of the axis of the rotation of the wheel, the'side edges and of the nib'inset forming the cutting edges. The diagonally sloped front advancing face 23 of the nibinset 22 thus presents the cutting edge as in advance of the cutting edge 25 as the cutting wheel rotates. The cutting edge25 is inclined fromthe hub section I l to the arcuate extremity it along a substantially straight line and thus presentsa substantially straight cutting edge. The advance cutting edge 26 has an arcuate or outwardly bulging contour which extendsfrom the tip edge 18 toward the crotch end 2'! of the cutting face. The diametrical length r of the curvilinear or arcuate cutting edge 25 should approximate the depth .of thegroove to be out.

It will be noted by referring to Fig; VlZI that the arcuatecutting edgeiZt is inclined at a greater angle with respect to themedial line ofthewheel designated as line s in Fig. VII, than the straight cutting edge 25. Assuming for example that'the groove cutting wheel is designed to groove 2. laminated plywood panel to permit the sections to be formed into a true right angle, thestraigh-t cutting edge 25 is inclinedto the medial lines at an angle approximately '35" to 40, while the outwardly bulging or arcuate edge 26 :has its crest point 28 inclined .at an angle of approximately to to the medial line s; and an imaginary chord line i drawn between "the ends or the .arcuate out line 26 would extend at an angle of approximately 45" to the medial line .9.

It will be further noted by referringto Figs. V, VI and VII that the alternating cutting arms l3 and iii present their arcuate cuttingtedge 25 on what might be called the left hand side of the wheel, and the intermediate cutting arms It and I6 present their arcuate cutting edge 26 on the right hand sideof the wheel. Likewise the cutting arms l3 and 15 present their straight cutting edge 25 on the right hand side of the wheel and the intermediate cutting arms l4 and it present their straight cutting edge 25 on the fleft hand side of the wheel. Thus it will be appreciated that when the groove cutting wheel is rotated to cut the laminated plywood panel, the cutting arms l3 and It will cut a groove having a straight inclined side face on the right hand side thereof and an arcuate side face on the left hand side thereof, andthe intermediate cutting arms I G and I6 traveling along the same groove wil'lgive the right hand face of the groove an arcuate contour. It will also be appreciated that as the panel is advanced under the rotating cutting wheel and in contact therewith, each of the cutting arms will cut an incremental slice from the front end of the groove and remove the sliced material therefrom. Due to the sloped inclination of the advancing face:23, the advance arcuatecutting edge '25 will have a more pronounced cutting effect than the following. straight cutting edge. 25. It is therefore preferable .to rotate the cutting wheel .at suflicientiy high speed with respect to the movement of the panel thereunder, so that the straight andmoreblunt cuttingedge 25 is not substantially relied upon to out the panel, and the advance arcuate cutting edges 28, which are presented on alternate sides of the successive advancing cutting :arms, perform the cutting work. When the :panel material has passed to the rear of the cutting wheel, both side faces of the groove will be of aroua-te cross sectional shape.

Assuming for example that the metal clad laminated plywood sectionsare to be finally shaped in right angular relationship as shown in Fig. :IX, the wood layers I and 3 which are cut in the .direction of the grain'will present slightly arcuate ends I and 3 and will remain substantially as out. The wo'odlayer 2 cut transversely of the run of the grain will present ibloomed .or brushed out .endsii extending-into the groove A. When the :panel'sections are bent to their intended right angular relationship, ;a joint 2 is formed as shown more particularly in Fig. IV

'whereinthe brushed out ends? of the intermediate wood layer 2 will be in tight abutment,

and the ends 3" of the outer woodlayer .3 will be in abutmentat their outer extremity, assat c. The joint e thus formed presents an interior space adequate to receive and contain .the

bloomed out ends 2" of the transversely .cut

plywoodlayer 2. The interiorspace of thejoint 2 may be packed with asuitable bonding adhesive.

The improved groove cutting wheelwill perform its function. of forming a groove in laminated plywood to :permit shaping or forming .of the sections to predetermined accurate shape, even though the inner and outer wood. layers of the plywood base sheet. are cut transversely the run of the grain. There is shown in Figs. I and Xca groove B but with this groove cutting wheel and wherein the groove B extends transversely of the grain of the inner and outer wood layers I and 3 and substantially parallel of the grain of the intermediate wood layer '2. Due to the arcuate shapingof theside faces of thegroova-the panel sections may be formed into their intended ac curate angular arrangement as shown in Fig. XI even though the out ends 1'' of the .wood layerl and the out ends 3" of the wood layer '3 have bloomed or brushed out into the groove. Since the fibers of the brushed" ends I' and 3" of layers .1 and .3 are to a certain extent flexible and deformable, the panels can be accurately shaped whenspace at the joint is-provided to permit such deformation.

Suchspaceis provided by the-concave cutends 2" of the intermediate .woodlayer -2 which-rd mains substantially as cut, and consequently provided ,arslight cavity between the ends :2", forming a joint 2' asshown in Fig. XI. This cavity between the spacedends 2 of ood layer .2 permits .of certain bending or bulging movement of .the brushed ends 1" and .3 into this cavity.

Fiuthermorasince the bloomed ends 1' and '3' of the wood layers l and 3 have beencut witha certaincavity by the curvilinear cutting edge 23 of the grooving wheel, there remainsa morerlimited but yet clearly definable space between the cut ends I' and 3' into which the brushed fibers may lodge. The space within the interior of the joint 2' may also be packed with a suitable bonding adhesive, x.

It will thus be appreciated that laminated plywood sections may be shaped to their intended angular relationship by forming the groove with generally arcuate wall surfaces in which the side faces are slightly concave. For example, if we assume as shown in Fig. XII that the intended angularity between the sections be designated by a predetermined angle 9, the groove is then so cut so that an angle g will be presented between the imaginary incline chord lines It extending from the valley of the groove 9 to the top corner edges thereof. The concave out side faces 7' defined by the curvilinear cutting edges of the grooving wheel are spaced from their respective imaginary chord lines 71. Since the imaginary chord lines 71. will coincide when the panel sections are shaped to their intended angular relationship, the cavity 1: defined between each arcuate wall surface 7' and the adjacent imaginary chord line h provides the necessary space to receive the bloomed or brushed out ends of those wood layers which are cut transversely of the grain. Since the fibers of the brushed out ends of the transversely cut -i layers are to a certain degree flexible, the fibers in the brushed out ends will flex and become accommodated to the cavity 1; provided therefor, thereby permitting the panel sections to be shaped to their intended angular relationship irrespective of the number of Wood layers in the laminated plywood base sheet, and irrespective of which layers have been transversely out.

It is thus seen that this improved groove cutting wheel possesses characteristics which permit the grooving of laminated plywood panels in a manner to insure predetermined accurate angular formation of the panel sections. Any unfilled cavity space between the grooved ends of the panel sections may be filled with a suitable bonding adhesive which gives strength to the joint.

While certain novel features of the invention have been disclosed herein, and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

I claim:

1. An improved metal clad laminated plywood panel construction havin sections thereof extending at a predetermined corner forming angle with respect to one another with the metal facing sheet forming a continuous and unbroken metal facing for one side of the laminated plywood backing, said sections presenting a biconvex joint defined between the adjacent cut ends of the laminated plywood layers, said out ends extending down to the metal facing sheet and meeting in a relatively sharply defined angle around which said metal facing sheet is bent, said adjacent out ends being generally arcuate in shape with the exterior and interior extremities thereof in firm abutment, the interior of said joint presenting an open biconvex space for the reception of the bloomed ends of the transversely cut plywood layers.

' 2. An improved metal clad laminated plywood panel construction having sections thereof ex tending at a predetermined corner forming angle with respect to one another with the metal facing sheet forming a continuous and unbroken metal facing for one side of the laminated plywood. backing, said sections presenting a biconvex joint defined between the adjacent out ends of the laminated plywood layers, said out ends extending to the metal facing sheet and meeting in a relatively sharply defined angle around which said metal facing sheet is bent, said adjacent cut ends being generally arcuate in shape with the exterior and interior extremities thereof in firm abutment, the interior of said joint presenting an open biconvex space having curvilinear faces for the reception of the bloomed ends of the transversely cut plywood layers, and a bonding adhesive within said joint.

3. An improved metal clad laminated plywood panel designed to be shaped into sections which extend at a predetermined corner forming angle with respect to each other, said metal clad plywood panel comprising a plywood backing having a metal facing sheet adhesively bonded to one face thereof, said plywood backing comprising a plurality of adhesively bonded wood veneer layers with the grain fibres of at least one of said layers extending in a crossing direction to the grain fibres of the adjacent layer, a generally V-shaped groove cut extending substantially through the plywood backing with the valley point of the groove adjacent the inner surface of the metal facing sheet, each of the opposite inclined faces of the groove being cut to present an arcuately convex curvature extending from the oute edges to the valley point of the roove.

4. An improved metal clad laminated plywood panel designed to be shaped to present sections which extend at a predetermined corner forming angle with respect to each other, said metal clad plywood panel comprising a plywood backing having a metal facing sheet adhesively bonded to one face thereof, said plywood backing comprising a plurality of adhesively bonded wood Veneer layers with the grain fibres of at least one of said layers extending in a crossing direction to the grain fibres of the adjacent layer, a generally V-shaped groove out extending substantially through the laminated plywood layers with the valley point of the groove adjacent the inner surface of the metal facing sheet, each of the opposite inclined faces of the groove being cut to present an arcuately convex curvature extending from the outer edge to the valley point thereof, the convex curvature of said inclined groove faces being such that imaginary straight line chords drawn from the valley point of the groove to the outer edge of each of said inclined side faces will be inclined with respect to each other at an angle which substantially equals the intended angular arrangement of the formed panel sections with the valley point of the groovedefining the line of bend.

GLENN H. NORQUIST.

REFEKENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,162,52 l Staley et al -Nov. 30, 1915 1,484,175 Elmendorf Feb. 19, 1924 1,669,667 Levine May 15, 1928 1,846,881 Lewis Feb. 23, 1932 1,381,734 Lewis Oct. 11, 1932 2,149,882 Clements Mar. '7, 1939 2,253,219 Alexander Aug. 19, 1941 

